Industrial Internet of Things (IIoT) is the subclass of IoT in the industrial sector which enables various devices, sensors, and controllers to collect and process data [1]}. Similarly, blockchain is another emerging technology which was introduced by Satoshi Nakamoto in 2008 for virtual currency [2]}. Blockchain is distributed ledger in which each transaction is recorded, and each peer duplicates the ledger in a consistent manner. The consistency is achieved through a consensus mechanism in which every transaction is cryptographically verified and added sequentially to the chain which is agreed by all participants of the network [3]}. In this way, it maintains a distributed, consistent, and temper-proof record with the attractive features of transparency, verification, and traceability. Generally, based on the participants access to the shared ledger, blockchain can be classified into two types which are permissioned and permissionless. In permissioned blockchain, the shared ledger can be accessed by selected participants whereas in permissionless blockchain each participant can access the shared ledger and take part in consensus [4]}[5]}.
